Charge-separation in panchromatic, vertically positioned bis(donor styryl)BODIPY-aluminum(iii) porphyrin-fullerene supramolecular triads

Niloofar Zarrabi; Christopher O. Obondi; Gary N. Lim; Sairaman Seetharaman; Benjamin G. Boe; Francis D'Souza; Prashanth K Poddutoori

doi:10.1039/c8nr06649c

Charge-separation in panchromatic, vertically positioned bis(donor styryl)BODIPY-aluminum(iii) porphyrin-fullerene supramolecular triads

Niloofar Zarrabi, Christopher O. Obondi, Gary N. Lim, Sairaman Seetharaman, Benjamin G. Boe, Francis D'Souza, Prashanth K Poddutoori

Chemistry & Biochemistry

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29 Scopus citations

Abstract

Three, broad band capturing, vertically aligned supramolecular triads, R₂-BDP-AlPorF₃←Im-C₆₀ [R = H, styryl (C₂H₂-Ph), C₂H₂-TPA (TPA = triphenylamine); ← = coordinate bond], have been constructed using BODIPY derivative (BDP, BDP-Ph₂ or BDP-TPA₂), 5,10,15,20-tetrakis(3,4,5-trifluorophenyl)aluminum(iii) porphyrin (AlPorF₃) and fullerene (C₆₀) entities. The C₆₀ and BDP units are bound to the Al center on the opposite faces of the porphyrin: the BDP derivative through a covalent axial bond using a benzoate spacer and the C₆₀ through a coordination bond via an appended imidazole. Owing to the bis-styryl functionality on BDP, the constructed dyads and triads exhibited panchromatic light capture. Due to the diverse absorption and redox properties of the selected entities, it was possible to demonstrate excitation wavelength dependent photochemical events. In the case of the BDP-AlPorF₃ dyad, selective excitation of BDP resulted in singlet-singlet energy transfer to AlPorF₃ (k_EnT = 1.0 × 10¹⁰ s^-1). On the other hand, excitation of the AlPorF₃ entity in the BDP-AlPorF₃←Im-C₆₀ triad revealed charge separation leading to the BDP-(AlPorF₃)⁺-(C₆₀)^- charge separated state (k_CS = 2.43 × 10⁹ s^-1). In the case of the Ph₂-BDP-AlPorF₃ dyad, energy transfer from ¹AlPorF₃∗ to ¹(Ph₂-BDP)∗ was witnessed (k_EnT = 1.0 × 10¹⁰ s^-1); however, upon assembling the supramolecular triad, (Ph₂-BDP)-AlPorF₃←Im-C₆₀, electron transfer from ¹AlPorF₃∗ to C₆₀ (k_CS = 3.35 × 10⁹ s^-1), followed by hole shift (k_HS = 1.00 × 10⁹ s^-1) to Ph₂-BDP, was witnessed. Finally, in the case of the TPA₂-BDP-AlPorF₃←Im-C₆₀ triad, only electron transfer leading to the (TPA₂-BDP)⁺-AlPorF₃←Im-(C₆₀)^- charge separated state, and no energy transfer, was observed. The facile oxidation of Ph₂-BDP and TPA₂-BDP compared to AlPorF₃ in the latter two triads facilitated charge separation through either an electron migration or hole transfer mechanism depending on the initial excitation. The charge-separated states in these triads persisted for about 20 ns.

Original language	English (US)
Pages (from-to)	20723-20739
Number of pages	17
Journal	Nanoscale
Volume	10
Issue number	44
DOIs	https://doi.org/10.1039/c8nr06649c
State	Published - Nov 28 2018

Bibliographical note

Funding Information:
This work was supported by startup grants from the University of Minnesota Duluth, to PPK, and by the National Science Foundation (Grant No. 1401188) to FD. We thank Prof. Steven Berry (University of Minnesota Duluth) for helping us in collecting the ESI mass data.

Publisher Copyright:
© 2018 The Royal Society of Chemistry.

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title = "Charge-separation in panchromatic, vertically positioned bis(donor styryl)BODIPY-aluminum(iii) porphyrin-fullerene supramolecular triads",

abstract = "Three, broad band capturing, vertically aligned supramolecular triads, R2-BDP-AlPorF3←Im-C60 [R = H, styryl (C2H2-Ph), C2H2-TPA (TPA = triphenylamine); ← = coordinate bond], have been constructed using BODIPY derivative (BDP, BDP-Ph2 or BDP-TPA2), 5,10,15,20-tetrakis(3,4,5-trifluorophenyl)aluminum(iii) porphyrin (AlPorF3) and fullerene (C60) entities. The C60 and BDP units are bound to the Al center on the opposite faces of the porphyrin: the BDP derivative through a covalent axial bond using a benzoate spacer and the C60 through a coordination bond via an appended imidazole. Owing to the bis-styryl functionality on BDP, the constructed dyads and triads exhibited panchromatic light capture. Due to the diverse absorption and redox properties of the selected entities, it was possible to demonstrate excitation wavelength dependent photochemical events. In the case of the BDP-AlPorF3 dyad, selective excitation of BDP resulted in singlet-singlet energy transfer to AlPorF3 (kEnT = 1.0 × 1010 s-1). On the other hand, excitation of the AlPorF3 entity in the BDP-AlPorF3←Im-C60 triad revealed charge separation leading to the BDP-(AlPorF3)+-(C60)- charge separated state (kCS = 2.43 × 109 s-1). In the case of the Ph2-BDP-AlPorF3 dyad, energy transfer from 1AlPorF3∗ to 1(Ph2-BDP)∗ was witnessed (kEnT = 1.0 × 1010 s-1); however, upon assembling the supramolecular triad, (Ph2-BDP)-AlPorF3←Im-C60, electron transfer from 1AlPorF3∗ to C60 (kCS = 3.35 × 109 s-1), followed by hole shift (kHS = 1.00 × 109 s-1) to Ph2-BDP, was witnessed. Finally, in the case of the TPA2-BDP-AlPorF3←Im-C60 triad, only electron transfer leading to the (TPA2-BDP)+-AlPorF3←Im-(C60)- charge separated state, and no energy transfer, was observed. The facile oxidation of Ph2-BDP and TPA2-BDP compared to AlPorF3 in the latter two triads facilitated charge separation through either an electron migration or hole transfer mechanism depending on the initial excitation. The charge-separated states in these triads persisted for about 20 ns.",

author = "Niloofar Zarrabi and Obondi, {Christopher O.} and Lim, {Gary N.} and Sairaman Seetharaman and Boe, {Benjamin G.} and Francis D'Souza and Poddutoori, {Prashanth K}",

note = "Funding Information: This work was supported by startup grants from the University of Minnesota Duluth, to PPK, and by the National Science Foundation (Grant No. 1401188) to FD. We thank Prof. Steven Berry (University of Minnesota Duluth) for helping us in collecting the ESI mass data. Publisher Copyright: {\textcopyright} 2018 The Royal Society of Chemistry.",

year = "2018",

month = nov,

day = "28",

doi = "10.1039/c8nr06649c",

language = "English (US)",

volume = "10",

pages = "20723--20739",

journal = "Nanoscale",

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publisher = "Royal Society of Chemistry",

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T1 - Charge-separation in panchromatic, vertically positioned bis(donor styryl)BODIPY-aluminum(iii) porphyrin-fullerene supramolecular triads

AU - Zarrabi, Niloofar

AU - Obondi, Christopher O.

AU - Lim, Gary N.

AU - Seetharaman, Sairaman

AU - Boe, Benjamin G.

AU - D'Souza, Francis

AU - Poddutoori, Prashanth K

N1 - Funding Information: This work was supported by startup grants from the University of Minnesota Duluth, to PPK, and by the National Science Foundation (Grant No. 1401188) to FD. We thank Prof. Steven Berry (University of Minnesota Duluth) for helping us in collecting the ESI mass data. Publisher Copyright: © 2018 The Royal Society of Chemistry.

PY - 2018/11/28

Y1 - 2018/11/28

N2 - Three, broad band capturing, vertically aligned supramolecular triads, R2-BDP-AlPorF3←Im-C60 [R = H, styryl (C2H2-Ph), C2H2-TPA (TPA = triphenylamine); ← = coordinate bond], have been constructed using BODIPY derivative (BDP, BDP-Ph2 or BDP-TPA2), 5,10,15,20-tetrakis(3,4,5-trifluorophenyl)aluminum(iii) porphyrin (AlPorF3) and fullerene (C60) entities. The C60 and BDP units are bound to the Al center on the opposite faces of the porphyrin: the BDP derivative through a covalent axial bond using a benzoate spacer and the C60 through a coordination bond via an appended imidazole. Owing to the bis-styryl functionality on BDP, the constructed dyads and triads exhibited panchromatic light capture. Due to the diverse absorption and redox properties of the selected entities, it was possible to demonstrate excitation wavelength dependent photochemical events. In the case of the BDP-AlPorF3 dyad, selective excitation of BDP resulted in singlet-singlet energy transfer to AlPorF3 (kEnT = 1.0 × 1010 s-1). On the other hand, excitation of the AlPorF3 entity in the BDP-AlPorF3←Im-C60 triad revealed charge separation leading to the BDP-(AlPorF3)+-(C60)- charge separated state (kCS = 2.43 × 109 s-1). In the case of the Ph2-BDP-AlPorF3 dyad, energy transfer from 1AlPorF3∗ to 1(Ph2-BDP)∗ was witnessed (kEnT = 1.0 × 1010 s-1); however, upon assembling the supramolecular triad, (Ph2-BDP)-AlPorF3←Im-C60, electron transfer from 1AlPorF3∗ to C60 (kCS = 3.35 × 109 s-1), followed by hole shift (kHS = 1.00 × 109 s-1) to Ph2-BDP, was witnessed. Finally, in the case of the TPA2-BDP-AlPorF3←Im-C60 triad, only electron transfer leading to the (TPA2-BDP)+-AlPorF3←Im-(C60)- charge separated state, and no energy transfer, was observed. The facile oxidation of Ph2-BDP and TPA2-BDP compared to AlPorF3 in the latter two triads facilitated charge separation through either an electron migration or hole transfer mechanism depending on the initial excitation. The charge-separated states in these triads persisted for about 20 ns.

AB - Three, broad band capturing, vertically aligned supramolecular triads, R2-BDP-AlPorF3←Im-C60 [R = H, styryl (C2H2-Ph), C2H2-TPA (TPA = triphenylamine); ← = coordinate bond], have been constructed using BODIPY derivative (BDP, BDP-Ph2 or BDP-TPA2), 5,10,15,20-tetrakis(3,4,5-trifluorophenyl)aluminum(iii) porphyrin (AlPorF3) and fullerene (C60) entities. The C60 and BDP units are bound to the Al center on the opposite faces of the porphyrin: the BDP derivative through a covalent axial bond using a benzoate spacer and the C60 through a coordination bond via an appended imidazole. Owing to the bis-styryl functionality on BDP, the constructed dyads and triads exhibited panchromatic light capture. Due to the diverse absorption and redox properties of the selected entities, it was possible to demonstrate excitation wavelength dependent photochemical events. In the case of the BDP-AlPorF3 dyad, selective excitation of BDP resulted in singlet-singlet energy transfer to AlPorF3 (kEnT = 1.0 × 1010 s-1). On the other hand, excitation of the AlPorF3 entity in the BDP-AlPorF3←Im-C60 triad revealed charge separation leading to the BDP-(AlPorF3)+-(C60)- charge separated state (kCS = 2.43 × 109 s-1). In the case of the Ph2-BDP-AlPorF3 dyad, energy transfer from 1AlPorF3∗ to 1(Ph2-BDP)∗ was witnessed (kEnT = 1.0 × 1010 s-1); however, upon assembling the supramolecular triad, (Ph2-BDP)-AlPorF3←Im-C60, electron transfer from 1AlPorF3∗ to C60 (kCS = 3.35 × 109 s-1), followed by hole shift (kHS = 1.00 × 109 s-1) to Ph2-BDP, was witnessed. Finally, in the case of the TPA2-BDP-AlPorF3←Im-C60 triad, only electron transfer leading to the (TPA2-BDP)+-AlPorF3←Im-(C60)- charge separated state, and no energy transfer, was observed. The facile oxidation of Ph2-BDP and TPA2-BDP compared to AlPorF3 in the latter two triads facilitated charge separation through either an electron migration or hole transfer mechanism depending on the initial excitation. The charge-separated states in these triads persisted for about 20 ns.

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Charge-separation in panchromatic, vertically positioned bis(donor styryl)BODIPY-aluminum(iii) porphyrin-fullerene supramolecular triads

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